LMCS/LMDS networks comprise a plurality of suitably arranged and configured transmitters operating on a frequency assignment basis. Such networks typically operate using QAM, QPSK, or some other digital modulation scheme. The networks are designed to minimise problems of intersymbol interference (ISI) at receiving sites where two or more signals could potentially be received.
There are a number of frequency assignment techniques known to the industry including:    (1) frequency division, in which an allocated spectrum is divided to form sets of frequencies which are applied to a cell structure in such a fashion that adjacent nearby cells operate on sufficiently different frequencies to avoid ISI;    (2) signal polarisation, which can effectively create or extend the number of available frequencies; and    (3) half channel interleaving, which can be used with some modulation schemes to allow a particular frequency to be reused in nearly adjacent cells.
It has been proposed to carry multiple video channels on such systems. In some countries, one or more bands around 26, 27 or 28 GHz have been reserved, whilst in others, the reserved bands are around 38 to 40 GHz. At these frequencies, the propagation of radio waves is relatively directional.